The new and improved catalysts of this invention are prepared by depositing on a finely divided and difficult to reduce inorganic oxide selected from silica, alumina, thoria, zirconia, titania, magnesia and/or mixtures thereof an organic chromium compound and then activating the resulting mixture in a non-oxidizing inert or reducing atmosphere at elevated temperatures up to about 2000.degree. F. followed by subjecting the activated catalyst to an oxidizing gas to burn off the carbon residue and to modify or improve the characteristics of the activated catalyst. This invention is also effective in improving the performance of such catalysts wherein the support is first chemically modified with metallic elements including zirconium, titanium and others. It has been found experimentally that a black color formed on the catalyst during activation is due to carbon deposits which are presumed to result from the decomposition of the organic chromium compound during the non-oxidative pyrolysis step. The carbon deposits are substantially removed by burning in an oxidizing gas and the resulting catalysts give much improved performance in 1-olefin polymerization. Notably and significantly improved are catalyst activity, solid polymer color of polymers produced with the new catalyst, and various other desirable polymer physical properties such as melt index, shear response, and melt elasticity.